Irradiation apparatus and method

ABSTRACT

An irradiation apparatus particularly well suited to the irradiation of food at or near the point of consumption includes an irradiation chamber, one or more ionizing radiation sources such as x-ray tubes, and a rotating food support. In one embodiment, one or more x-ray sources are disposed axially in relation to the support. In another, one or more x-ray sources are disposed radially in relation to the support. The position of the x-ray sources in relation to the food may also be varied depending on the size of the food.

BACKGROUND

The present invention relates to the irradiation of food products usingionizing radiation such as x-rays. The invention is also applicable toirradiation in industrial, medical, sterilization or other fields inwhich efficient irradiation of materials is desired.

Diseases caused by contaminated food are one of the most widespreadhealth problems in both the developed and developing countriesthroughout the world. The majority of these diseases, caused bybiological agents such as bacteria, parasites and viral agents, aremanifest by symptoms such as diarrhea, abdominal pain, nausea andvomiting. The Center for Disease Control estimates that foodbornediseases cause approximately 76 million illnesses, 325,000hospitalizations, and 5,000 deaths annually in the United States(Food-Related Illness and Death in the United States, Center for DiseaseControl and Prevention, 1999.) More alarming is the fact that many ofthe pathogens of real concern today were not even recognized as causesof foodborne illness just twenty years ago.

These and other issues have been addressed by irradiation. The amount ordose of radiation to which food is exposed is a function of the durationof exposure to radiation, the density of the food, and the energyemitted by the irradiator. Relatively low doses can control trichnia inpork, inhibit ripening and extend shelf life of fruits and vegetables,and control insects and other pests. Higher doses control bacteria inpoultry and other foods. Still higher doses control microorganisms inherbs, spices, teas, and other dried vegetables.

The following is exemplary of pathogen sensitivity in meat:

D₁₀ Value Log Reduction 6D₁₀ Reduction Pathogen (kGy) at 4.5 kGy Dose(kGy) Camphylocbacter 0.18 25 1.1 Clostridium 0.586 7.7 3.5 E. coliO157:H7 0.25-0.45 10-18 1.5-2.7 Listeria 0.40-0.64   7-11.2 2.4-3.8Salmonella 0.48-0.70 6.4-9.4 2.9-4.2 Staphylococcus 0.45 10 2.7Toxoplama 0.40-0.70 6.4-11  2.4-4.2 gondii Trichinella 0.30-0.60 7.5-15 1.8-3.6 spiralis

D₁₀ values represent the x-ray dose that will result in a ten-foldreduction in pathogen concentration. Considering E. coli bacterium, theabove chart shows that an irradiation dose of 4.5 kGy would ensure atleast a ten billion-fold or 10 log reduction (log reduction column inthe foregoing table) in concentration.

Over forty governments have established regulations permitting theirradiation of a wide variety of foods. Within the United States, theFood and Drug Administration (FDA) has approved the use of ionizingradiation for pathogen reduction, food preservation and disinfection forapproximately 80% of the food supply. Applications now underconsideration for ready-to-eat foods and shellfish will, if approved asexpected, allow for irradiation of virtually all foods excepting finfish. Regulations governing the irradiation of food are published at 9CFR 179.26. Exemplary doses for certain foods are summarized below:

Maximum Dose Food Type (kGy) Pork 1 Spices, vegetable seasonings andherbs 30 Fruit and fresh vegetables 1 Poultry (fresh, frozen ormechanically 3 separated) Red meat (fresh) 4.5 Red meat (frozen) 7.0Shell eggs 3

The FDA has granted clearance for food irradiation using ionizingradiation from three sources that have been shown to produce equivalentpathogen reductions. The approvals cover gamma rays from radioactivecobalt-60 or cesium-137, linear accelerators producing electrons atenergies below 10 million electron volts, and x-rays generated frommachine energies of less than 5 million electron volts.

While there are a number of large scale facilities in the United Statesthat employ radiation technology for sterilizing of a range of productssuch as medical supplies, only a fraction are dedicated to foodproducts. Common characteristics of these systems are their bulk size,scale and cost. Another common characteristic is a continuous conveyorsystem that supplies the food product into the irradiation chamber.Examples of such systems are disclosed in U.S. Pat. No. 4,866,281 toBosshard, entitled Irradiation Plant; U.S. Pat. No. 5,554,856 to Bidnyy,et al., entitled Conveyor-Type Unit for Radiation Sterilization; andU.S. Pat. No. 4,481,652 to Ransohoff, entitled Irradiation Device.

Capital costs for large, production scale systems are substantial.Furthermore, the radiation sources must be shielded, often by severalfeet of concrete, and still provide access for food products deliveredon the continuous conveyor system. To minimize per pound irradiationcosts for food products, the units are often operated continuously withthe typical capability to process one hundred thousand pounds of fooddaily. To achieve these efficiencies, the units must be located incentral food processing or distribution centers that are remote from theconsumer.

Machines utilizing electrons to sterilize food such as manufactured byBioSterile Technology, Inc. of Fort Wayne, Ind. are the most compact ofthese large production scale systems as a result of the limitedpenetration capability of its charged electrons. In this instance theirradiation chamber with a volume of 3.3 cubic feet is but a smallcomponent of the overall system dimensions. Nonetheless, even with arelatively small irradiation chamber, the overall size and cost of suchsystems remains substantial.

U.S. Pat. No. 6,212,255 to Kirk, entitled System for X-Ray Irradiationof Blood describes a smaller scale, batch irradiator for x-ray beamirradiation of blood contained within a transfusion bag. The bag isplaced within a 15.5×12×4 cm canister which limits the bag to a maximumthickness of 4 cm. A first x-ray tube is positioned to irradiate the bagfrom a first side, and a second tube is positioned to irradiate the bagfrom the opposite side. An alternate embodiment includes a single x-raytube, which is used to irradiate the first side of the bag for apreselected time period. Thereafter, the bag is rotated, and theopposite side is irradiated for an equal period of time. In eitherembodiment, the distance from the output port of the x-ray tube(s) tothe near side of the bag is 23 cm, and the beam geometry is selected sothat the beam diameter is at least 15.5 cm at this distance.Accordingly, the extent of the x-ray beam is sufficient to irradiate theentire 15.5×12 cm extent of the bag. One disadvantage of such a systemis its bulk, as the distance between the output ports of the two x-raytubes is some 50 cm. Of this distance, the blood to be irradiatedoccupies at most only 4 cm, with the remainder being air. As theintensity of the x-radiation received by the blood is inversely relatedto the square of the separation, the intensity of the radiation receivedby the bag is also relatively small. Moreover, a substantial portion ofthe x-rays does not impinge on the blood and therefore does notcontribute to its irradiation.

U.S. Pat. No. 6,180,951 B 1 to Joehnk, et al., entitled Process forIrradiating Producing Constant/Depth Dose Profile discloses an apparatusfor irradiating a target material wrapped around an annular reel. Thereel is rotated about an axis perpendicular to the sweep of a beam ofionizing radiation. The objective of the arrangement is to create eithera constant or a linear relationship between the depth of the targetmaterial and the received dose. Joehnk teaches that the perpendicularrelationship been the axis of rotation of the reel and the direction ofbeam sweep is critical to the function of the invention. The electronbeam source is located at a distance from the target material such thatbeam extent is greater than the target material extent. In addition, thetarget material must be wrapped around the reel and occupies only aportion of the reel's diameter. In one exemplary embodiment, a materialhaving a thickness of 1.5 inches (3.81 cm) is disposed on a 10 inchdiameter (25.4 cm) core; in another a material having a thickness of 1inch (2.54 cm) disposed on an 8 inch (20.3 cm) diameter core. Thesefactors likewise decrease the efficiency and increase the relative sizeof the apparatus.

Aspects of the present invention address these matters, and others.

SUMMARY

According to a first aspect of the present invention, a food irradiationapparatus includes an x-ray source which generates and x-ray beam, and arotating support disposed in proximity to the x-ray beam. Rotation ofthe support causes successive portions of the food to be exposed to thefirst radiation beam.

According to a more limited aspect of the invention, the x-ray source isdisposed axially in relation to the food.

According to a more limited aspect of the invention, the apparatusincludes a second x-ray source disposed on a side of the supportopposite from the first x-ray source. According to a still more limitedaspect of the present invention, the support rotates about an axis ofrotation and the x-ray sources are equidistant from the axis ofrotation. According to another more limited aspect of the invention, thesupport is disposed between the first x-ray source and the food and thesecond x-ray source is disposed in relation to the food such thatrotation of the support causes successive portions of the food to beexposed to the second radiation beam. The distance between the secondx-ray source and the support may be adjustable.

According to another more limited aspect of the present invention, thesupport rotates about an axis of rotation and the relative distancebetween the axis of rotation and the support is adjustable.

According to another more limited aspect of the invention, the x-raysource is disposed radially in relation to the food. In a still morelimited aspect, the support rotates about an axis of rotation and thedistance between the first x-ray source and the axis of rotation isadjustable. The relative positions of the food and the radiation sourcein a direction parallel to the axis of rotation may also be adjustable.

According to another more limited aspect of the invention, means fordetermining a dimension of a container supported by the support isincluded.

According to another aspect of the present invention, an irradiationapparatus includes a rotating support for supporting an objected to beirradiated and a first source of ionizing radiation. The source isdisposed axially in relation to the object. Rotation of the supportimproves a uniformity of the radiation dose received by the object.

According to a more limited aspect of the invention, the radiationsource is offset from the axis of rotation of the support. According toanother more limited aspect of the present invention, the apparatusincludes means for varying a position of the radiation source in atleast one of an axial or radial direction. According to another morelimited aspect, a sensor for determining a dimension of the object maybe provided.

According to another aspect of the present invention, a batchirradiation apparatus includes an irradiation chamber and a door whichprovides access to the chamber for selectively inserting and removingthe object. The apparatus also includes an x-ray source which generatesa radiation beam that impinges on a portion of the object and a meansfor varying the relative positions of the x-ray source and the object sothat the radiation beam impinges on successive portions of the object.

According to a more limited aspect of the invention, the objectcomprises food and the apparatus includes an operator input device foridentifying the type of food.

According to another aspect of the present invention, a method forirradiating a quantity of food typically encountered in the homeincludes inserting the quantity of food into an irradiation chamberthrough an access port, turning on an x-ray source, varying the relativepositions of the x-ray source and the food such that successive portionsof the food are exposed to the x-rays generated by the source, turningoff the x-ray source, and removing the quantity of food from theirradiation chamber through the access port.

One advantage of the present invention is that an apparatus and methodparticularly well suited to irradiating food at or near the point of usemay be provided. Another advantage is that quantities of food as aretypically encountered in residential and residential/small scalecommercial environments may be economically irradiated.

Another advantage is that a relatively small and economical irradiationapparatus may be provided.

Still other aspects and advantages of the present invention will beunderstood by those skilled in the art upon reading and understandingthe attached description.

DRAWINGS

FIG. 1 is a perspective view of an irradiation apparatus.

FIG. 2 depicts an axial arrangement of an irradiation apparatus.

FIG. 3 depicts an axial arrangement of an irradiation apparatus.

FIG. 4 depicts dose distributions at the surface of an object.

FIG. 5 depicts depthwise dose distributions in relation to an object.

FIG. 6 depicts a radial arrangement of an irradiation apparatus.

FIG. 7 depicts a radial arrangement of an irradiation apparatus.

FIG. 8 depicts an x-ray source having a large planar anode.

FIG. 9 depicts an x-ray source having a cylindrical anode.

DESCRIPTION

Referring to FIG. 1, an irradiation apparatus 10 particularly wellsuited for use at or near the point of consumption such as in the home,a restaurant, or retail environment is shown. The apparatus 10 includesan irradiation chamber 14. In a preferred embodiment for irradiating thefood volumes typically encountered in such environments (e.g., meat orlike materials weighing on the order of 0.5-1 kg), the irradiationchamber has a volume less than about 2 cubic feet. Disposed within theirradiation chamber 14 is a substantially non-radiation attenuativerotating support 15 such as a platter or a topwise support from which anobject may be suspended. The irradiation chamber 14 is shielded by anx-ray attenuative material such as lead. Access to the irradiationchamber is provided via a shielded door 16. While shown as hinged,access may be provided by a sliding door or other suitable arrangement.An operator interface 18 includes a suitable display 20 and operatorinput device 22 such as a membrane keyboard for accepting instructionsfrom and providing operational information to a user. The unit ispreferably powered by a conventional residential/commercial electricpower such as a 120 15/20A or 240 volt 40A circuit through a power cord24. Suitable power supplies, control electronics, mechanicalarrangements and the like are likewise disposed within the apparatushousing 12. In particular, the controller preferably includesconventional microprocessor based circuitry, though the controller mayalso be implemented via suitable digital and/or analog circuitry. Toreduce the size of the housing 12, items such as the power supplies maybe packaged separately and connected via suitable wiring.

An embodiment wherein the x-ray sources 26 a, 26 b are arranged axiallyin relation to the support 15 and an object 30 supported thereby isdepicted in FIG. 2. First and second radiation sources 26 a, 26 b suchas x-ray tubes generate respective first and second radiation beams 28a, 28 b directed toward the irradiation chamber 14. A material to beirradiated 30 such as food (including any associated containers) may beplaced on the rotating support 15, which rotates about an axis ofrotation 32. While the object 30 is depicted as being cylindrical, theobject and/or its containers may take other shapes as well. The x-raysources 26 a, 26 b are offset from the axis of rotation 32 and locatedon opposite sides of the object 30. Dose received by the object 30 maybe monitored by one or more dosimeters 16.

The x-ray tube 26 a, 26 b include a cathode 34 and an anode 36 disposedwithin a housing 38. A large voltage is maintained between the cathode34 and anode 36, on the order of 100 kV. Accelerating within a vacuummaintained within an evacuated envelope, electrons generated at thecathode 34 strike the positively charged anode 36 and generate x-raybeams 28 a, 28 b. X-rays are preferentially directed out of the tubes 26a, 26 b through a window with an intensity maximum along the primarybeam central axis in a substantially conical radiation beams 28 a, 28 b.An x-ray tube designed for non-destructive material testing such as theMXR165 tube manufactured by Comet, Ag of Liegefeld-Bern Switzerland isexemplary of a suitable x-ray source.

In addition to characteristic radiation that is dependent on the anodecomposition, the x-ray tubes 26 a, 26 b produce a continuous spectrum ofradiation, so-called Bremsstrahlung radiation, that ranges up to amaximum of the applied tube voltage. It is desirable that the low energyx-rays be preferentially filtered, for example by a 1 mm aluminum filter40 a, 40 b, or other suitable attenuator, particularly for x-ray tubes26 a, 26 b operating with an accelerating voltage of 150 kV or greater.

The foregoing arrangement provides for the efficient use of theradiation generated by the radiation sources 26 a, 26 b, which areplaced in close proximity to the irradiated material 30. In particular,the separation between the sources 26 a, 26 b is minimized andpreferably as close as possible to the material 30. As the distancebetween the source and material is reduced, the x-ray intensity alongthe central beam axis increases by an inverse square law. To provide forthe most efficient use of the generated x-rays, the distance is chosensuch that substantially all emitted radiation is received by thematerial. With such an arrangement, however, the dose uniformity at thematerial 30 surface is localized and produces a non-uniform dosedistribution such that only a portion of the object 30 is exposed to theradiation beams 28 a, 28 b.

Turning now to FIG. 3, this non-uniformity may be understood for anx-ray source 26 centered 5 cm above the surface of a 25 cm diameterobject 30 where the x-ray beam intensity decreases as the cos² of theangle from the central beam axis. The dose distribution at the nearsurface of the object for such an arrangement is shown by plot 42 ofFIG. 4, where the x-axis represents the distance from the center of theobject. With the convention that the maximum dose at any point on thesurface the object is denoted as D_(max) and the corresponding minimumby D_(min), the ratio D_(max)/D_(min) may be taken as a measure of doseuniformity. In the illustrated case, the ratio at the product surfaceexceeds 5.

Returning for a moment to FIG. 2, dose uniformity in the foregoingarrangement can be improved by positioning the x-ray source 26 b so thatit is offset from the axis of rotation 32, for example by a distanceequal to the radius of the object 30. If the object 30 remainsstationary, however, only a portion to the object is exposed to thex-ray beam 28 b.

The object 30 is rotated about axis of rotation 32 at an angularfrequency that exceeds the inverse of the total exposure time to ensureat least one complete rotation through 360 degrees during theirradiation period. The radial dose distribution for such an arrangementis shown by plot 44 of FIG. 4, again where the x-ray beam intensitydecreases as the cos² of the angle from the central beam axis. As willbe appreciated, the dose distribution is substantially more uniform thanthat of plot 42. While the foregoing has focused on radiation source 26b, positioning radiation source 26 a in a complementary fashion producesa similar result at the other surface of the object. The relativepositions described above may be varied, depending on the desired doseuniformity and irradiation time, the shape and distribution of the x-raybeam 28, the dimensions and shape of the object 30, x-ray utilizationefficiency, and the like.

It is desirable that irradiation be accomplished in a time frame similarto that for conventional microwave cooking. As an example, consider anx-ray source delivering a dose of 0.8 kGy/minute at a distance of 5 cm.Irradiation of 1 kg of unfrozen red meat to a dose of 4 kGy can beaccomplished in approximately 5 minutes.

Dose uniformity in the depth direction is determined in part by theattenuation of the radiation in the object 30. Turning now to FIG. 5,plot 46 approximates the depthwise dose distributions where the object30 is irradiated from a single side, and where the x-axis representsdistance from the surface of the object. As illustrated by plot 48,depthwise uniformity may be improved by irradiating the object from thesecond side.

While a device having two radiation sources 26 a, 26 b disposed onopposite sides of the object has been described, it will be appreciatedthat one of the radiation sources may be omitted. In one suchembodiment, the source 26 and the rotating support 15 are arranged sothat the distance between the source and the object 30 is substantiallyconstant irrespective of the depth of the object (e.g., the support 15is disposed between the source 26 and the object 30). Alternately, oneor both of the radiation sources 26 a, 26 b may be movable in the axialdirection depending on the depth of the object 30 so as to maintain thedesired distance between the source(s) 26 a, 26 b and the object 30, forexample using a motor drive arrangement. Such an arrangement isparticularly advantageous where the device will be used to irradiatefood or other objects having differing axial dimensions.

One or both of the radiation beams 28 a, 28 b may also be movable in theradial direction depending on the radial extent of the object 30, forexample using a motor drive arrangement operatively connected to thesources 26 a, 26 b. Such an arrangement is particularly advantageouswhere the device will be used to irradiate food or other objects havingdiffering radial dimensions.

According to yet another embodiment, two or more radiation sources 26may be located on the same side of the object.

Turning now to FIG. 6, the x-ray source 26 may be disposed radially withrespect to the object 30. By analogy to the axial arrangement describedabove, the x-ray source may be located at a distance from the axis ofrotation 32 which exceeds the approximate radial extent of the object30. In one embodiment, the x-ray source 26 is located at as near aspossible to the object, e.g. at approximately the radial extent of theobject. Again, the object 30 is rotated about the axis of radiation 32to improve dose uniformity.

Turning now to FIG. 7, two or more x-ray sources 26 a, 26 b may bedisposed radially in relation to the object. Such an arrangement has theadvantage of improving axial dose uniformity without requiring orminimizing axial movement of the x-ray beams 28 Depending on the axialextent of the object 30, the x-ray beam 28 and the object 30 may movedrelative to each other to improve axial dose uniformity. Relative axialmotion may be achieved by a drive arrangement operatively connected tothe x-ray source 26.

In addition, the radiation source(s) 26 a, 26 b and the object 30 may bemovable relative to each other in the radial direction to maintain adesired distance between the source(s) and the object, for example usinga motor drive arrangement connected to the support 15 or the source 26.Such an arrangement is particularly advantageous where the device willbe used to irradiate food or other objects with different radialdimensions.

The axial and/or radial extent of the object 30 may be determined invarious ways. For example, dimensional information may derived fromdosimeters 16 which provide low resolution image-like information.Dimensional information may also be derived from information specific tofood product containers of various sizes. Thus, the apparatus may bedesigned to work with a series of containers having predefined sizes,where the user is instructed to place the object 30 in the containermost closely approximating the object's dimensions. The containers maythemselves provide dimensional data, for example by unique mechanicalkeys or interlocks, electrical contacts, or magnetic elements whichcooperate with corresponding devices associated with the irradiationapparatus 10. Alternately, the containers may be coded with dimensionalinformation (e.g., small, medium, large, or 3 cm, 5 cm, 10 cm, etc.) orcolor coded with user asked to enter the information through theoperator interface 18. According to yet another embodiment, positioningmembers may be provided with the apparatus 10. Position measurementdevices such as potentiometers indicate the location of the positioningmembers. Upon placing the food or the container on the support 15, theuser then positions the straps or guides in contact therewith so thatthe approximate dimensions are known.

In certain instances, it may be preferable to reduce the air pressurewithin the irradiation chamber 14 or a closer-fitting food container tominimize undesirable organoleptic effects. A partial vacuum may beeffected by a roughing pump or through water aspiration. Further, it maybe desirable to reintroduce an artificial atmosphere to surround thefood product during irradiation. Suitable ports and valves for providingand/or recycling the atmosphere may optionally be provided.

It may be desirable to combine the effects of irradiation with otherprocedures in the food preparation process. Accordingly, yet anotherembodiment of the present invention combines technologies for such foodprocessing in a single appliance. Specifically, a provision fordirecting ultrasonic energy into the food product is provided for thebenefit of tenderizing meat or other products. Ultrasonic radiation maybe further analyzed to determine additional food properties includingdensity or position within the irradiation chamber. Incorporation of amicrowave-generating device operating in the frequency range ofconventional microwave ovens allows for the heat treatment or cooking ofthe food products. The irradiation appliance may also be combined todeliver a desired cooking level with the combination of conventional,convection or halogen based heating oven technology.

Still other configurations of the x-ray source 26 are contemplated. Inparticular, increasing the x-ray source 26 focal spot size reduceslocalized anode heating, increases x-ray beam coverage, and reducesdistance dependent intensity reduction. Referring to FIG. 8, the sourceincludes a large planar anode 36 constructed of conventional thicktarget material such as tungsten and may be of a reflective ortransmission type thickness. While shown as a rectangular surface, anynumber of planar geometries are possible. As a practical method, thecathode filament may be distributed in a manner to enhance current flownear the perimeter of the anode to account for its truncation. As isappreciated by those skilled in the art, the corresponding cathode andsurrounding vacuum housing are not shown for simplicity. The anode 36 ispreferably displaced from the object 30 by a distance approximatelyequal to the depth of the object. Depending on the relative sizes of thex-ray beam and the object, acceptable dose uniformity may be achievedwithout rotation of the object 30.

Referring to FIG. 9, the large area anode 36 may be extended to includea cylindrical three-dimensional geometry. In this configuration, object30 is surrounded by the cylindrical anode 36. As is appreciated by thoseskilled in the art, the cylindrical cathode and surrounding vacuumhousing are not shown for simplicity.

The foregoing discussion has assumed that the x-ray source(s) 26 remainstationary while the support 15 rotates. Equivalent results may beachieved by causing the x-ray source(s) to rotate about the object.Moreover, the effective position of the x-ray source(s) 26 may be variedby magnetically deflecting the electron beam before it strikes the x-raytube anode 36.

In operation, the food to be irradiated, together with any desiredcontainer, may be placed on the object support 15 and the door 16closed. The operator interface 18 facilitates entry of desiredirradiation parameters. For example, the user may input informationrelating to the type of food, quantity of food, and/or desired radiationdose. Dose information may be provided by direct entry of the desireddose or irradiation time, or by entry of a desired effect such asripening rate reduction, shelf-life extension, or pathogen reduction.The processing electronics in turn determines the desired irradiationtime and other relevant parameters. Moreover, the relative positions ofthe object being irradiated 30 and the x-ray source(s) may be adjustedas necessary.

During irradiation, the support 15 is rotated about its axis of rotation32 so that successive portions of the object 30 are exposed to theradiation beam(s) 28. Any required axial or other motion of theradiation beams 28 is also accomplished. Under control of the controlelectronics, irradiation continues for the calculated time or until thedosimeter(s) 16 indicate that the desired dose has been achieved(information from one or more dosimeters may be combined to improveaccuracy of the dose measurement).

Optional tenderizing, microwaving, or other processing may also occur.Status information is provided to the user via the operator interface18. Upon completion of the process, the object 30 may be removed fromthe irradiation chamber 14.

The invention has been described with reference to the preferredembodiments. Of course, modifications and alterations will occur toothers upon reading and understanding the preceding description. It isintended that the invention be construed as including all suchmodifications an alterations insofar as they come within the scope ofthe appended claims or the equivalents thereof.

We claim:
 1. A food irradiation apparatus comprising: a first x-raysource which generates a first radiation beam a rotating supportdisposed in proximity to the first x-ray source, wherein rotation of thesupport causes successive portions of food supported by the support tobe exposed to the first radiation beam, wherein the support is disposedbetween first x-ray source and the food; a second x-ray source disposedon a side of the support opposite from the first x-ray source whereinthe distance between the second x-ray source and the support isadjustable.
 2. A food irradiation apparatus comprising: a first x-raysource which generates a first radiation beam; a rotating supportdisposed in proximity to the first x-ray source, wherein rotation of thesupport causes successive portions of food supported by the support tobe exposed to the first radiation beam, wherein the support rotatesabout an axis of rotation and the distance between the axis of rotationand the first x-ray source is adjustable.
 3. The apparatus of claim 2wherein the first x-ray source is disposed radially in relation to thefood.
 4. The apparatus of claim 3 wherein the support rotates about anaxis of rotation and the relative position of the food and the firstradiation source in a direction parallel to the axis of rotation isadjustable.
 5. The apparatus of claim 2 further including means fordetermining a dimension of a container supported by the support.
 6. Theapparatus of claim 1 wherein the x-ray source comprises an x-ray tubeincluding a cathode and an anode.
 7. The apparatus of claim 1 furtherincluding an irradiation chamber sized to receive a quantity of foodtypically encountered at or near the point of consumption and whereinthe x-ray source comprises an x-ray tube having a cathode and an anode.8. The apparatus of claim 2 wherein the x-ray source comprises an x-raytube including a cathode and an anode.
 9. The apparatus of claim 2further including an irradiation chamber sized to receive a quantity offood typically encountered at or near the point of consumption andwherein the x-ray source comprises an x-ray tube having a cathode and ananode.
 10. An irradiation apparatus comprising: a rotating support forsupporting an object to be irradiated, which support rotates about anaxis of rotation; a first source of ionizing radiation for irradiatingthe object, the source being disposed axially in relation to the object,wherein rotation of the support improves a uniformity of the radiationdose received by the object; a sensor for determining a dimension of theobject.
 11. The apparatus of claim 10 wherein the apparatus includes anoperator input device for identifying the type of food.
 12. Theapparatus of claim 10 further including an irradiation chamber sized toreceive a quantity of food typically encountered at or near the point ofconsumption.
 13. An irradiation apparatus comprising: a rotating supportfor supporting and object to be irradiated, which support rotates aboutan axis of rotation, a first source of ionizing radiation forirradiating the object, the source being disposed axially in relation tothe object, wherein rotation of the support improves a uniformity of theradiation dose received by the object; means for varying a position ofthe first radiation source relative to the support in at least one of anaxial or radial direction.